Method and apparatus for processing soluble crystals

ABSTRACT

SOLUBLE CRYSTALS ARE TREATED IN A CENTRIFUGE DRUM WHICH ROTATES AT A PREDETERMINED PREPHERAL SPEED. THE CRYSTALS ARE EJECTED THROUGH AN OUTLET OF THE DRUM INTO A RECEIVER OF ANNULAR CONFIGURATION AND TUBULAR CROSS-SECTION, HAVING A CIRCUMFERENTIAL SLOT THROUGH WHICH THE CRYSTALS ARE EJECTED INTO IT. A LIQUID IN WHICH THE CRYSTALS ARE SOLUBLE IS CONTAINED IN THE RECEIVER AND ROTATES AT A SECOND PERIPHERAL SPEED WHICH IS SMALLER THAN THE PERIPHERAL SPEED OF THE CENTRIFUGE DRUM.

May 1, 1973 HEDL 'R 3,730,769

METHOD AND APPARATUS FOR PROCESSING SOLUBLE CRYSTALS Filed May 26, 1971 2 Shets-Sheet 1 I'NVENTOR Benn"; Flfljbk'l' May a LQ v umuon AND APPARATUS FOR PROCESSING smJuum-z (:nYs'h/m;

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United States Patent 3,730,769 METHOD AND APPARATUS FOR PROCESSING SOLUBLE CRYSTALS Bernhard Fiedler, Grevenbroich, Germany, assignor to Maschinenfabrik Buckau R. Wolf AG., Munich, Germany Filed May 26, 1971, Ser. No. 147,128 Claims priority, application Germany, May 27, 1970, P 20 25 828.0 Int. Cl. C131? 1/06 US. Cl. 127--19 16 Claims ABSTRACT OF THE DISCLOSURE Soluble crystals are treated in a centrifuge drum which rotates at a predetermined peripheral speed. The crystals are ejected through an outlet of the drum into a receiver of annular configuration and tubular cross-section, having a circumferential slot through which the crystals are ejected into it. A liquid in which the crystals are soluble is contained in the receiver and rotates at a second peripheral speed which is smaller than the peripheral speed of the centrifuge drum.

BACKGROUND OF THE INVENTION The present invention relates generally to the treatment of soluble crystals, and more particularly to a method for treating soluble crystals, especially sugar crystals, and to an apparatus for carrying out the method.

It is known to provide continuously operating centrifuges, especially in the sugar-making art, in which sugar crystals are separated from liquid and ejected from the centrifuge drum. It is customary, however, to use centrifuges of this type only in circumstances in which the crystals subsequently after the centrifuging are either again dissolved or otherwise admixed With liquids, because of the strong tendency of such drums to damage the crystalline structure. The byproducts which are not salable, such products as so-cal'led B-sugar and affinades are dissolved in water, thinned juices or the like, and are then subjected to a cooking process. For this purpose conveying devices, vessels for solution or vessels for admixing are required.

Such intermediate or semi-finished products as B-sugar as well as the affinades have a tendency-especially on ejection from the centrifugeto cake and form knots or walls, as a result of the high ejection speed and the residual syrup film which adheres to the crystals. The crystals which impinge at the wall of the centrifuge housing at high speed tend to cake on this wall and to build up a deposit or layer which in turn eventually clogs the outlet housing and makes it necessary again and again to clean the centrifuge in a time-consuming manner. This, of course, necessitates that the centrifuge be shut down so that continuous operation is not possible.

The realization of these disadvantages is of course not new. Accordingly, the prior art has proposed in German Pat. 1,285,410 to provide elastic baffie surfaces or flexible impingement elements into the outlet housing of the centrifuge. Dutch Pat. 123,575 suggests to surround the outlet flange which is provided at the outlet of the centrifuge drum with a collecting ring. Although these proposed approaches provide some relief in the problems mentioned, it has been found that none of them are capable of entirely eliminating the formation of balls or knots formed from adhering crystals.

This, however, is particularly disadvantageous because when the crystals are subsequently to be dissolved, these knots will dissolve only with great difficulty, thereby increasing the time required for the dissolution process. The knots also significantly increase the difficulties involved in making a mash and forming a magma, because non-dissolved knots make the subsequent working of the magma difficult, especially during automatic closing or dispensing of predetermined quantities of the latter. Differences in the quality of the crystals also cannot be avoided under such circumstances. Parenthetically it is pointed out that the term magma refers to an artificial filling mass which can be used in various ways known to those skilled in the art.

SUMMARY OF THE INVENTION It is an object of the present invention to overcome the disadvantages inherent in the prior art.

More particularly it is an object of the present invention to provide an improved method in which the formation of knots or balls of crystals during the aforementioned processing is reliably and completely avoided.

Still more particularly it is an object of the present invention to provide such a method which not only avoids these difiiculties but can be used in a continuously operating centrifuging process.

A concomitant object of the invention is to provide an apparatus for carrying out the method.

In pursuance of the above objects, and of others which will become apparent hereafter, one feature of the invention resides in my novel method according to which soluble crystals are treated in a centrifuge drum which rotates at a first peripheral speed. The crystals are ejected through an outlet of a drum into a'receiver containing a liquid in which the crystals are soluble, and the liquid is rotated in the receiver at a second peripheral speed which is smaller than the first peripheral speed of the drum.

By resorting to the present invention I assure that the crystals which enter the receiver from the drum will be intercepted at and by the surface of the liquid rotating in the receiver, and will be caused to rotate along with this liquid. As a result of this they no longer have the opportunity to contact the inner wall of the receiver at which heretofore the formation of knots and caking took place, and which actually facilitated these phenomena. Moreover, the crystals in the method and apparatus according to the present invention become dissolved in the rotating body of liquid in the receiver, if this body is water or a thinned juice. On the other hand, if the body is a super-saturated solution, then a mash is the result. In any case, the contents of the receiver can be supplied without any difficulties and with the simplest of conveying meansfor instance a conduit with an interposed pumpfrom the receiver to the cooking or boiling stations, or to other stations where they undergo different and further processing. It is also no longer necessary to provide special vessels for dissolving the crystals nor to provide special vessels for forming a mash.

It is already 'known in the art, namely from German Pat. 1,482,717, to provide a construction in which a body of liquid in ring form rotates With a centrifuge, to form of sugar crystals a mash. However, this body of liquid rotates with the centrifuge drum and as a result has the same speed of rotation as the drum. Because of this the body of liquid is subjected to high centrifugal forces which make it impossible for the crystals to form a mash, due to the different specific weights of syrup and crystals with a result that a separation or sedimentation of crystals and syrup takes place.

By contrast, the present invention causes the body of liquid to rotate in a stationary annular member, with the rotation of the body of liquid being caused only by the air friction resulting at the outlet flange of the centrifuge drum. It is possible to influence the rotation of the body of liquid by having the outlet flange enter into the body of liquid to a greater or lesser degree. However, under all circumstances the body of liquid will rotate at a peripheral speed which is lower than that of the centrifuge drum itself, so that a dissolution and/or formation of mash of the crystals in the body of liquid can readily take place.

The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a section taken on line 1-1 of FIG. 2 illustrating an apparatus for carrying out the present invention;

FIG. 2 is a plane view of the centrifuge drum of the apparatus in FIG. 1;

FIG. 3 is a section taken on line III-III of FIG. 2 with the outlet flange extended;

FIG. 4 is asection taken on line III--HI of FIG. 2, but illustrating an arrangement of supplementary nozzles; and

FIG. 5 is a section on line III-III of FIG. 2 illustrating a rotating-liquid chamber.

DESCRIP IlION OF THE PREFERRED EMBODIMENTS Discussing now the drawing in detail, and firstly FIGS. 1 and 2, it will be seen that the centrifuge drum 1- which may be driven in entirely conventional manner and with conventional means well known to those skilled in the artis of conical configuration and identified with reference numeral 1. It diverages in upward direction, being mounted so that its outlet end is located at the upper side. At its outlet end the drum has an outlet or discharge flange 2 which exends into an annular slot 5 formed in the wall of a tubular cross-section receiver 4 which is of annular configuration and is stationaril'y mounted. The slot '5 is delimited in this embodiment by collecting baffles 7 and 8 which extend in parallelism with one another and which extend inwardly and outwardly beyond the edges bounding the slot 5. The baffles 7 and 8, and especially those portions which extend into the interior of the element 4, are necessary to prevent the ring or body of liquid 6 which rotates in the interior of the element 4, from being expelled through the slot 5.

The centrifuge 1 rotates at high speed, as is conventionally known to those skilled in the art. Because of this high speed the flange 2 extending through the slot 5 into the interior of the element 4 causes within the latter a turbulence, with the resulting air friction effecting rotation of the body 6 about the axis of the annular element 4. Because of the fritcion of the liquid of the body 6 with the inner wall of the element 4, however, the peripheral speed at which the body 6 rotates is lower than the peripheral speed at which the flange 2 itself rotates with the drum 1.

In FIG. 2 I have illustrated one possiblility for supplying the liquid into the interior of the element 4, that is the liquid which is required for forming the ringshaped body 6 therein. In FIG. 2 th'ere are provided a plurality of inlet nipples 9, 10 and 11 which are arranged tangentially at the outer periphery of the element 4 and connected with non-illustrated supply conduits through which the liquid is supplied.

In FIG. 4 I have illustrated an embodiment which is ditferent in that supplementary nozzles 13 are provided which are connected with an annular supply conduit 14 beneath a cover plate 3. These nozzles 13 eject jets 18 of liquid which are ejected into the interior of the centrifuge drum. The same result is obtained when the nozzles 13 are arranged above the plate 3 and when the jets 13 are directly aimed into the interior of the element 4 through the slot 5. The nozzles 13 may be utilized by 4 themselves, or they may be used in conjunction with the nipples 9-11 if desired. The nozzles 13, and/or the nipples 9-11, may extend radially or tangentially with reference to the circumference of the element 4, or they may have radial and tangential components of orientation.

In FIG. 5 I have illustrated an embodiment in which there is secured to the lower side of the flange 3 a chamber 15 which rotates with the flange 2 and into which a stationary conduit 17 discharges liquid for forming the annular body 6. The liquid introduced into the chamber 15 will flow-as a result of the rotation of the chamber-- in upward direction along the outer chamber wall 19 and then issues via bores 16 in the flange 2 into the annular slot 5 and through the same into the interior of the element 4. Again, it is pointed out that the chamber 15 can be used by itself, or can be used in combination with the nipples 911 and conceivably also either with the nozzles 13 alone or with those in combination with the nipples 9-11.

In operation of the device according to the present invention, the sugar crystals which have been separated from the liquid of the suspension by centrifuging in the drum 1 (it will be understood that the invention is being explained herein on hand of an example in which sugar crystals are being separated) rise along the inner surface of the Wall of the drum, leaving the drum through the annular gap 20. From there the sugar crystals pass via the flange 2 into the interior of the element 4 where they are intercepted by the surface of the rotating body of liquid 6. As a result of this the sugar becomes either dissolved or forms a mash. The thus-produced magma (matrix) or clearing liquor (the difference depends upon whether the crystals are dissolved or become converted into mash) passes via the outlet nipple 12 into a non-illustrated conduit or conduit systems to be carried away for further processing or storage.

The outlet nipple 12 may be located above the central axes of the element 4, to assure that only fully dissolved crystals (or crystals which have fully undergone the mash-making process) will leave the outlet nipple 12 as overflow. Suitable throttling elements, such as flap valves or other types of valves of known construction, may be provided in the conduits which communicate with and receive liquid from the outlet nipple 12, in order to influence the flow of the liquid leaving the component 4 through the outlet nipple 12.

A comparison of FIGS. 3 and 5 will indicate that the flange 2 may extend to a greater or lesser depth into the interior of the component or element 4 through the gap 5, whereby the rotation of the body of liquid 6 therein is influenced, that is if the flange 2 extends deeper into the interior of the element 4, the body of liquid will rotate at higher circumferential or peripheral speed. A quantity of the liquid withdrawn from the body 6 can be recirculated in order to thereby influence the viscosity'of the body 6.

It will be appreciated that what I have illustrated herein are only some possible examples, and that this is not to be considered limiting in any sense. For instance, it is conceivable to provide a centrifuge drum having a horizontal axis rather than a vertical axis of rotation, in which case the element 4 could be mounted as a certain distance from the flange of the drum and a stationary body of liquid 6 could be provided. In this rase the liquid removed from the interior of the element 4 would then be withdrawn through a conduit provided in the lower regions of the element 4.

It will be nnderstood that each of the elements described above, or two or more together, may also find a useful application in other types of constructions differing from the types described above.

While the invention has been illustrated and described as embodied in the processing of soluble crystals, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention.

Without further analysis the foregoing will so fully reveal the gist of the present invention that others can by applying knowledge readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the following claims.

What is claimed as new and desired to be protected by Letters Patent is set forth in the appended claims:

1. In a method of processing soluble crystals particularly sugar crystals, the steps of treating soluble crystals in a centrifuge drum rotating at a first peripheral speed; ejecting the crystals through an outlet of the drum into a receiver containing a liquid in which said crystals are soluble; and rotating the liquid in said receiver at a second peripheral speed which is smaller than said first peripheral speed.

2. In a method as defined in claim 1; further comprising the steps of withdrawing quantities of said liquid from said receiver; and returning at least some of the withdrawn liquid into said receiver.

3. In an apparatus for processing soluble crystals, particularly sugar crystals, in combination, a continuously rotatable centrifuge drum having an outlet for ejection of soluble crystals which have been separated in said drum from a liquid in which they were suspended, and a flange surrounding the outlet; and an annular receiver of tubular cross-section surrounding said outlet and having a circumferential slot into which said flange extends, said receiver being adapted to contain a revolving body of liquid which rotates at lower speed than the drum and in which the ejected crystals are soluble.

4. In an apparatus as defined in claim 3, said slot being bounded by transversely spaced edge portions; and further comprising baflle members provided on said edge portions for preventing the escape of matter entering said slot from said outlet.

5. In an apparatus as defined in claim 4, wherein said baflle members extend in at least substantial parallelism with one another and with at least a portion of said flange.

6. In an apparatus as defined in claim 3; further comprising inlet means communicating with the interior of said receiver for admitting into the same a liquid in which said crystals are soluble.

7. In an apparatus as defined in claim 6, wherein said inlet means opens into said receiver radially of the latter.

8. In an apparatus as defined in claim 6, wherein said inlet means opens into said receiver tangentially of the latter.

9. In an apparatus as defined in claim 6, wherein said inlet means opens into said receiver at an angle which has a radial and a tangential component relative to said receiver.

10. In an apparatus as defined in claim 6, said inlet means comprising a plurality of circumferentially distributed inlets.

11. In an apparatus as defined in claim 6, said inlet means comprising as annular liquid chamber below said flange and rotatable with said drum, said flange comprising a plurality of axial bores communicating with said chamber.

12. In an apparatus as defined in claim 11, further comprising a stationary liquid supply conduit communicating with said chamber.

13. In an apparatus as defined in claim 6, said inlet means comprising a plurality of inlet nozzles separate from said receiver and located on an annular line having a smaller diameter than said receiver.

14. In an apparatus as defined in claim 13, said nozzles being oriented so as to discharge into said annular slot.

15. In an apparatus as defined in claim 13 further comprising an annular supply conduit connecting said nozzles for supplying liquid thereto.

16. In an apparatus for processing soluble crystals, particularly sugar crystals, in combination, a continuously rotatable centrifuge drum having an outlet; a flange surrounding said outlet; an annular receiver of tubular crosssection surrounding said flange and having a circumferential slot adapted to receive matter from said outlet; and a revolving body of liquid operative for dissolving said crystals, accommodated in said receiver.

References Cited UNITED STATES PATENTS 3,490,947 1/ 1970 Grieselhuber 127-19 978,238 12/1910 Trent 233--28 3,301,708 1/1967 Rotel 12756 X 3,650,465 3/1972 Grimwood 127-19 X JOSEPH SCOVRONEK, Primary Examiner S. MARANTZ, Assistant Examiner US. Cl. X.R. 

